The present invention relates to a technique for reducing the influence of indirect sound which is output by a speaker and which reaches the listener after being reflected from a wall of a room or the like.
Sound output by a speaker directly reaches the sound receiving point where the listener is located, and further indirectly reaches the point after being reflected from a wall surface of a room or the like. The indirect sound which indirectly reaches the point is mixed with the direct sound which directly reaches the point, so that the listener listens to sound which is different from the sound that is actually output by the speaker. Particularly, indirect sound which, after direct sound reaches, reaches with being delayed by a time period that is shorter than the auditory temporal resolution is heard not as reverberant sound in the room, but as sound in which the quality is changed. In order to reduce the influence which is exerted on the quality of such indirect sound at the sound receiving point, therefore, a technique for applying a correcting process on sound output by a speaker has been developed (for example, JP-A-5-49098 and JP-A-60-223295).
A configuration which performs a correcting process as in JP-A-5-49098 and JP-A-60-223295 requires an FIR (Finite Impulse Response) filter. When an FIR filter is used, an accurate control is enabled, but the computational complexity is increased. When the sampling frequency is high, particularly, the computational complexity is very large.